Attempts will be made to analyze the regulation of glycosylation in murine plasmacytoma cells in order to further characterize the importance of this cellular process for membrane localization and secretion of immunoglobulins. Control of the synthesis of N-glycosidically linked oligosaccharides will be examined at the level of nucleotide sugars, the initial glycosyl donors for the formation of lipid-linked oligosaccharide intermediates. Nucleotide sugar levels, nucleotide sugar flow rates, lipid-linked oligosaccharide synthesis and pool sizes, glycoprotein synthesis, and immunoglobulin secretion will be measured in MOPC 315 cells (an IgA-producing murine plasmacytoma) and in a nonsecretory variant previously determined to have only membrane IgA. Nucleotide sugar pyrophosphatase activity will be measured in both cell lines. Also, this activity will be measured under experimental conditions designed to modulate its activity. Changes in enzyme activity will be correlated with nucleotide sugar levels, glycoprotein synthesis, and secretion to access its importance in the regulation of glycosylation. In addition, the oligosaccharide units of IgA and of cell surface glycoproteins derived from MOPC 315 cells and the variant 315/P cells will be characterized in order to compare these structures in two related lymphoid cell lines with such different requirements for glycosylation.